It is conventional to discharge particulate or bulk material from rail hopper cars by introducing a carrier liquid, usually water, into the car so as to form a slurry, which then is removed from the car through conduit pipes from a sump in the bottom portion thereof. This slurry unloading procedure preferably is used with materials which are at least partially soluble in the carrier liquid. However, slurry unloading can be used with insoluble particulate materials which are also capable of slurry formation, if a sufficient throughput of carrier liquid is used. When the method is used for soluble materials, including sodium chlorate, it is preferred to use insufficient carrier liquid to dissolve the material, but merely sufficient to form a pumpable slurry, so as to decrease the discharge time and minimize solvent use.
Sodium chlorate is shipped in crystalline form with some residual moisture. During shipping, the sodium chlorate tends to become a hard, almost concrete-like mass in the rail car, as residual moisture is driven off in summer heat or frozen in winter cold. This physical form of the sodium chlorate makes difficult the offloading of the sodium chlorate from the rail car.
Conventional hopper cars for slurry unloading generally have used nozzles mounted in the side walls of the hopper compartment, from which streams of liquid are passed into the car for turbulent admixture with the material to be unloaded. However, formation of the slurry has been found to be uneven. In the slurry formation, a portion of the particulate matter close to the nozzles dissolves and forms a true solution, this solution then forms a hollowed-out portion in the body of the particulate matter and other particulate matter from above collapses into the solution forming a slurry.
Canadian Pat. No. 951,359 describes a nozzle arrangement for a hopper car in which the nozzles are arranged to direct streams of liquid which impinge in an upward direction against the junction between a side wall and an end wall of the commodity-carrying compartment. This arrangement is intended to form a flow pattern in which liquid passes along the walls and tends to separate the particulate matter from the walls, so as to form a slurry in rapid and convenient manner. In addition, directing the liquid streams against the wall junctions is intended to cause the streams to spread along the walls and clean them.
Hopper cars constructed in accordance with Canadian Pat. No. 951,359 are in commercial use and have been used by the assignee of this patent application in the delivery of sodium chlorate to its customers at various locations in North America. Although these hopper cars have been found to be an improvement on previous hopper cars, the sparger system employed still leaves residual caked-on masses of sodium chlorate which must be removed, typically using steam lances.
In addition, the sparger nozzles are prone to damage and breakage as a result of impact of lumps of the solid sodium chlorate during slurry formation. The presence of broken-off nozzles in the slurry is a danger to pumps used by the mill to off-load the slurry to storage and the remaining opening in the sparger emits a non-directional spray which is ineffective in effecting slurry formation.